The present invention relates to an improvement of a ball-point pen having a ball valve mechanism at the point, by pushing a writing ball at the pen point with an elastic body at all times, wherein a ball serving as a writing portion is prevented from slipping out and fitted loosely, in the state having a space of a proper size to ensure a channel of the ink. More specifically, the present invention relates to an improvement relating to solve drawbacks such as a play of the ball, writing characteristics, shock resistance, vibration starving or the like of ball-point pen with an oil-based or water-based ink or a clicking-type ball-point pen, having a medium viscosity ink.
Conventionally, as a ball-point pen type writing instrument, there can be mentioned: a so-called oil-based ball-point pen with an ink having a high viscosity (about 10,000 cp), using a higher alcohol solvent as a main solvent, is directly contained in an ink container tube; a so-called water-based ball-point pen with an ink having a low viscosity (from 2 to 3 cp), using water as a main solvent is stored in a bundle of fibers, referred to as slivers; and a neutral ball-point pen having intermediate properties of oil-based and water-based ball-point pens. Since the oil-based ball-point pen has a high viscosity, the manner that writing sensation is heavy, lots of blobbing is caused, and since the ink is directly stored, if air comes into the point, a trouble of back leaking of the ink is easily caused. On the other hand, the water-based ball-point pen has such disadvantages that the remaining amount of the ink cannot be confirmed, that the ink easily spreads out onto the face of a document, that since members such as slivers and intermediate feed do not discharge all the ink, the life span is short, and that barrel cylinder becomes thick. With the neutral ball-point pen for solving these drawbacks, back leaking can be almost resolved by means of a mechanism of prevention of back leaking, such as a ball valve. The present applicant has already proposed an invention of a neutral ball-point pen of a type in which a writing ball is pushed with a small load at all times toward inside of the pen point, but when adopting the invention for an actual writing instrument, drawbacks described below were found, and further improvement became necessary.
With a ball-point pen of a type in which the writing ball is pushed by an internal elastic body, there is a case where a ball seat and a point portion are worn away by the ball, with the progress of writing, and though the ink still remains, the ball slips out, thereby the ball-point pen cannot be used anymore for writing. In particular, in the case where a coloring agent of the ink is a pigment type ink with a solid fine powder being dispersed, or in the case where the ink is a water-based ink using water having poor lubricity as a base, or in the case where the oil-based ink is an ink having a viscosity of a medium level (from 10 to 5000 cp at 25xc2x0 C.), these drawbacks are easily caused, due to wear caused by the solid component, or because of discontinuity of the ink film which tends to occur during ball rotation. As measures against these, there has been considered a measure in which a material of the ball and a tip holder is changed to a material such as a stainless steel having a high hardness, but in that case, there are such disadvantages that machining of the tip holder becomes difficult in proportion to the hardness, and the pen point becomes expensive. Also, when an improvement is performed with an ink, if a lubricant is blended into the ink in a large amount, these disadvantages are alleviated. Due to the lubricant, however, the ink tends to cause spreading on the face of a document, and a drawback of forward leaking, that is, the surface tension of the ink decreases to make the pen point easy to be wet, and when the pen is turned downward, the ink leaks out from the pen point. Thus, it has been found that a simple improvement with an ink is also difficult.
Furthermore, for a ball-point pen using a volatile ink, an elastic body is provided for pushing the writing ball at all times in order to prevent an ink from being volatilized when the ball-point pen is not used for writing, or to prevent starving, or in the worst case, back leaking of the ink caused by the air caught up from the pen point due to an impact such as being dropped or the like, or a so-called forward leaking, that is, the ink is dripping from the pen point. When a pushing force was increased for improving the effect, the forward leaking preventing characteristics was improved, but internal wear and, in the worst case, slipping out of the ball were caused due to writing. In the case of a clicking-type ball-point pen, there is a further drawback that at the time of accommodating a writing element serving as a writing body, the writing element is accommodated with an impact to cause the ball much easier to slip out. Furthermore, when a diameter of the writing ball increases, it favors prevention of the wear, but starving becomes more easily caused due to an impact because of the air brought up from the tip, compared to the case of the writing ball with a small diameter. As a measure against these drawbacks, there is proposed a measure in which a rubber or a spring is inserted between the writing element and the inside of the barrel cylinder, for absorbing the impact. However, with this ball-point pen, there is caused a drawback in that the rubber or the like for absorbing the impact is deformed at the time of writing, causing the pen point to move back and forth, to thereby make writing difficult. Also, another drawback occurs in that since the number of parts increases and it is necessary to consider a method for fixation, the cost also increases.
In particular, with a so-called neutral ball-point pen using an ink having a viscosity intermediate between the oil-based ball-point pen and the water-based ball-point pen, the above-mentioned drawbacks are more likely to occur. However, though being rather insufficient as a ball-point pen, the neutral ball-point pen is put on the market, since other advantages thereof are recognized. Some invention of ball-point pens in which these drawbacks are solved have been proposed occasionally, however, it is still necessary to solve a drawback of wear within the pen point and a drawback of starving resulting from the low impact resistance, considering the productivity, the cost and correlation with the clicking mechanism, including a new demand arising from needs of bold or fine tips.
The present invention is directed to an improvement of a so-called ball-point pen type writing instrument, wherein a ball serving as a writing portion is fitted loosely to the inside a point assembly of popular type, in a state protruding from the point yet not to slip out, and more specifically, the present invention is directed to an improvement of a ball-point pen having an ink having a medium viscosity. A major object of the present invention is to solve a drawback that writing becomes impossible with the ink still remaining inside before the life span as a pen body is finished, while ensuring the writing sensation from the initial stage as writing proceeds. Moreover, another object of the present invention is to provide a writing instrument having excellent performance at a low cost, without requiring an ink of special blend or an advanced mechanism, by solving drawbacks such as starving due to a diameter of a writing ball, or starving and slipping out of the ball due to a return impact in the case of a clicking type ball-point pen, without sacrificing the productivity and performance of the ball-point pen.
The ball-point pen of the present invention devised to solve the above described drawbacks is so configured that a ball serving as a writing portion rotatably protrudes, at distal end while prevented from slipping out, and an ink is accommodated within an ink container tube. It is constructed such that the ink is led out onto a face of an outside document, from a ball which is rotatable and serving as a writing portion, through ink channels such as a plurality of channel grooves set to be a proper size within the pen point, a lateral play in the lateral direction, and a vertical play in which the ball can move so that the ink can be led in the vertical direction. The loosely fitted ball is prevented from slipping out by means of a front caulking by means of a plastic deformation and a rear ball seat, in the freely rotatable state. The ball is prevented from slipping out by means of a stable caulking by the optimization of the ball protrusion, the inner diameter and outer diameter of the caulking portion. As one example, at the time of caulking process, the inner diameter portion of the caulking portion is rather strongly caulked until abutting against the ball, to thereby form a seal face inside. In this case, if the seal face has a shape with approximately the same R as the ball, and a certain width over the whole periphery, the drawback of the forward leaking can further be solved. Moreover, while ensuring the vertical play, if a ball seat that becomes a rearward receiving face in the axial direction of the ball and has approximately the same R as the ball is provided, this becomes effective for solving the drawback of wear.
That is to say, a first gist of the present invention is a ball-point pen whose ball rotatably fitted loosely in the state of protruding outside from front end is restricted in its back and forth movement by a caulking portion at the front end and by a ball seat at rear end, comprising: a point assembly having an ink hole for leading the ink from the rear end side; an ink storing tube for directly storing a so-called medium viscosity ink whose ink viscosity at a normal temperature (23xc2x0 C.) is in a range of from 10 cp to 5000 cp; a channel groove constituted by a plurality of grooves communicating the ball seat and the ink hole, which is not penetrated through in the longitudinal direction; and an elastic body installed in a state that it cannot be pulled out such that it pushes the ball at the point directly or indirectly via a movable member at all times; wherein the following relation:
20xc2x7W less than P less than 75xc2x7W
is satisfied between a projection area W (mm2)) of a diameter of the writing ball and a pushing force P (g) of the elastic body.
A second gist of the present invention is a clicking-type ball-point pen according to the first gist, further comprising: a front opening from which a writing portion can be protruded at a front end of barrel cylinder, and a click bar serving as a protruding pushing portion at the rear end, and accommodating a writing element serving as a writing body within the bar, movably in the back and forth direction; wherein the writing element is constructed such that it is urged rearward at all times by a return spring; and that the following relation:
50xc2x7R less than S less than (50xc2x7R+20xc2x7P)
is satisfied among a ball pushing force P (g) within the point assembly and a pushing force S (g) of the return spring and a weight R (g) of the writing element.
A third gist of the present invention is a clicking-type ball-point pen according to the first gist, further comprising: a so-called double clicking-type clicking mechanism wherein the writing body is protruded for writing by pushing the click bar, and the writing body can subsequently be retracted by pushing the click bar again, characterized in that a rotator abutting against the writing element or backside of the writing element moves while rotating, between a moving distance L of the writing element from a protruding state at the time of writing to a retracted state at the time of non-writing, to thereby convert a part of the impact due to a pushing force of the return spring at the time of retraction into a rotation movement of a predetermined angle xcex8, and the following relations are satisfied:
5 mm less than L less than 10 mm, and 40 degrees less than xcex8 less than 160 degrees.
A fourth gist of the present invention is a ball-point pen according to the first gist, further comprising: a so-called double clicking-type clicking mechanism wherein the writing body is protruded for writing by pushing the click bar, and the writing body can subsequently be retracted by pushing the click bar again, characterized in that a rotator abutting against the writing element or backside of the writing element moves while rotating, between a moving distance L of the writing element from a protruding state at the time of writing to a retracted state at the time of non-writing, to thereby convert a part of the impact due to a pushing force of the return spring at the time of retraction into a rotation movement of a predetermined angle xcex8, and the following relations are satisfied:
5 mm less than L less than 10 mm, and 40 degrees less than xcex8 less than 160 degrees.
A fifth gist of the present invention is a clicking-type ball-point pen according to the second gist, further comprising: a so-called safety mechanism comprising an elastic clip outside a barrel cylinder, having a latch portion for protruding the writing body enabling to write, automatically retracing the writing element serving as the writing body when the clip is lifted for putting the ball-point pen in clothes, characterized in that all parts, that are separated behind the writing element in the state of writing and are bumped on each other and affected by the impact at the time of return, are made of a synthetic resin such as rubber, elastomer, plastic or the like, and at least one of the parts is constructed by a material having an internal loss xcex7, which is a vibration absorbing property, of not less than 0.02, and flexural modulus E that shows a rigidity of all the parts affected by the impact, of not less than 1,300 MPa.
A sixth gist of the present invention is a clicking-type ball-point pen according to the third gist, further comprising: a so-called safety mechanism comprising an elastic clip outside barrel cylinder, having a latch portion for protruding the writing body enabling to write automatically retracting the writing element serving as the writing body when the clip is lifted for putting the ball-point pen in clothes, characterized in that all parts, that are separated behind the writing element in the state of writing and are bumped on each other and affected by the impact at the time of return, are made of a synthetic resin such as rubber, elastomer, plastic or the like, and at least one of the parts is constructed by a material having an internal loss xcex7, which is a vibration absorbing property, of not less than 0.02, and flexural modulus E that shows a rigidity of all the parts affected by the impact, of not less than 1,300 MPa.
A seventh gist of the present invention is a clicking-type ball-point pen according to the fourth gist, further comprising: a so-called safety mechanism comprising an elastic clip outside a barrel cylinder, having a latch portion for protruding the writing body enabling to write automatically retracting the writing elements serving as the writing body when the clip is lifted for putting the ball-point pen in clothes, characterized in that all parts, that are separated behind the writing element in the state of writing and are bumped on each other and affected by the impact at the time of return, are made of a synthetic resin such as rubber, elastomer, plastic or the like, and at least one of the parts is constructed by a material having an internal loss xcex7, which is a vibration absorbing property, of not less than 0.02, and flexural modulus E that shows a rigidity of all the parts affected by the impact, of not less than 1,300 MPa.
As a first means for making the present invention effective as described above, an elastic body for urging the writing ball forward at all times is provided behind the writing ball, directly or indirectly via a piece movable between the elastic body and the writing ball, while the writing ball is prevented from slipping out by a caulking portion at front tip, thereby the elastic body is loosely fitted such that the forward of the elastic body cannot be pulled out by means of the writing ball, and the rear thereof cannot be pulled out by means of a caulking portion at the rear end of the point assembly and an internal step of a joint part at the rear of the point assembly. Here, the construction is such that the following relation:
20xc2x7W less than P less than 75xc2x7W
is satisfied between a projection sectional area W (mm2)) of the writing ball and a pushing force P (g) of the elastic body. That is to say, since the ball diameter and the projection area have a relation of squares, it is constructed such that as the diameter of the writing ball increases, a pushing load of the elastic body increases in proportion to a square.
As a second means of the present invention, after the first means is satisfied, it is mounted in the clicking-type writing instrument, such that the writing element is urged backward at all times by a return spring, and the following relation:
50xc2x7R less than S less than (50xc2x7R+20xc2x7P)
is satisfied among a writing element weight R, and a pushing force S of the return spring and a pushing force P of the elastic body within the point assembly.
As third and fourth means of the present invention, the mechanism of a clicking-type is a so-called double clicking type (or also referred to as kaan-type clicking), wherein protrusion and retraction at the point assembly from the inside of the barrel cylinder are repeated only by pushing with the clicking bar, and the rotation angle xcex8 at the time of returning from the protruding state to the retracted state is set to be 40 degrees less than xcex8 less than 160 degrees, while defining the stroke moving distance L of the clicking (the length of a difference between a length in the protruding state from the point assembly and a length at the time of retraction) is to be 5 mm less than L less than 10 mm, which is larger than the normal 4 mm.
Moreover, as means for alleviating the clicking impact at the time of return, all parts behind the writing element that are affected by the impact at the time of return are made of a synthetic resin such as rubber, elastomer, plastic or the like, and at least one of the parts is constructed by a material having an internal loss xcex7, which is a vibration absorbing property, of not less than 0.02, and flexural modulus E that shows a rigidity of all the parts affected by the impact, of not less than 1,300 MPa. Specifically, a ball-point pen with a pigment type water-based ink having an ink viscosity of from 10 cp to 5000 cp at 23xc2x0 C.xc2x15xc2x0 C., which is referred to as a neutral type, troubles such as back leaking and forward leaking are easily caused, thus a prevention mechanism is required, as well as wear becomes severe and furthermore it is necessary to ensure a large ink channel. In such cases, the effect of the present invention is especially anticipated.
The operation of the above-described will now be described. With the improvement achieved by the present invention, it becomes possible to prevent starving due to vibration, forward leaking and back leaking that are easily caused in a ball-point pen of a medium viscosity type, and to ensure high performance such as keeping balance among slipping out of the ball, starving at the time of strong impact and writing performance, which tends to cause a trouble in the case of a mechanism in which the writing ball is urged with a small force within the point assembly. The present invention provides a particularly effective operation for applied products such as for fine writing, for bold writing, for clicking-type and the like that are high in user""s demand. By satisfying the relation of 20xc2x7W less than P less than 75xc2x7W between a projection area W of a diameter of the ball and a pushing load P of the writing ball, no starving occurs due to vibrations, the writing performance is not deteriorated, which occurs when the ball becomes hard to rotate due to a too strong pushing force, and furthermore, slipping out of the ball due to being dropped or due to a clicking impact as well as a phenomenon that the pen tip wears due to writing does not occur. Moreover, in the case of a clicking type, there are drawbacks in that if the return pushing load S is too large, an impact force becomes big to cause a drawback such as starving or the like, or if the return pushing load S is too weak, the pen tip is clicked unintentionally due to vibration at the time of being carried or due to a light impact, to thereby cause the pen tip to protrude to stain clothes. When the pushing load S of the return spring is defined to be 50xc2x7R less than S less than (50xc2x7R+20xc2x7P) for alleviating or removing harmful effect of the return impact, the minimum return pushing load S is set by the weight R of the writing element and the maximum return pushing load S is set in proportion to the pushing load P of the writing ball within the point assembly described above, thereby a ball-point pen having no drawback can be obtained. That is to say, as weight of the writing element becomes heavier, larger return pushing load S is required, and as the pushing load P of the writing ball becomes longer, the impact resistance increases. Hence, the return pushing load S can be made large.
In the case of a double-clicking type ball-point pen, the moving amount of the writing element at the time of return acts not only on the vertical movement in the axial direction but also on the moving amount in the rotational direction utilizing a cam, and as a result, it has an effect as an impact reducing mechanism. With the present invention, when the moving amount L of the pen tip between protruding and retracting states is set to be a large stroke amount of from not smaller than 5 mm to more than 10 mm, by setting the rotation angle xcex8 to be 40 degrees less than xcex8 less than 160 degrees, which is larger than the normal rotation angle, for the effective operation of reducing the impact, thereby the writing element is retracted while rotating largely at the time of return, to alleviate the impact effectively. If the rotation angle xcex8 is not larger than 40 degrees, the movement of the writing element becomes close to a straight line to increase the impact value to the writing element, and if the rotation angle xcex8 is 160 degrees or larger, the rotation angle by one click becomes too large, and a practical writing instrument cannot be obtained. If the parts behind the writing element are made to be impact-absorbing parts, more effective operation can be expected. In general, however, those having a large coefficient of internal loss xcex7 showing the degree of impact absorption are soft and do not have a rigidity in many cases, and one that is simply soft cannot satisfy the function expected from its shape, and there are drawbacks in that it is necessary to specially arrange those parts as impact-absorbing parts, and furthermore, those parts are deformed even by a load at the time of writing, and the pen tip moves back and forth unsteadily at the time of writing. With the present invention, if the rigidity is 1,300 MPa or larger, the pen tip does not move back and forth with a writing pressure, and if the value of the internal loss xcex7 is 0.02 or larger, the ball-point pen has also an impact absorbency. Therefore, by forming the parts behind the writing element with a synthetic resin having a rigidity and a certain degree of vibration absorbency, and by forming at least one part with a material having a high impact absorbency, an effect of alleviating the impact at the time of return can be expected.
By constituting the ball-point pen as described above, the assembling feasibility, cost and stability of parts can be simultaneously satisfied.
Specifically, with a neutral ball-point pen having a low ink viscosity compared to an oil-based ball-point pen, the present invention can operate most effectively. Troubles such as forward leaking, back leaking and wear due to a large flow rate of ink and a difficulty to impart lubricity can be solved, and degree of freedom can be provided to the design of the ink, and as a result, the general performance of the pen body can be improved.